/*
 * (c) Copyright 2007, 2008, 2009 Hewlett-Packard Development Company, LP
 * (c) Copyright 2010 Talis Systems Ltd
 * All rights reserved.
 * [See end of file]
 */

package com.hp.hpl.jena.sparql.engine.iterator;

import java.util.Iterator ;
import java.util.Set ;

import com.hp.hpl.jena.sparql.algebra.Algebra ;
import com.hp.hpl.jena.sparql.core.Var ;
import com.hp.hpl.jena.sparql.engine.ExecutionContext ;
import com.hp.hpl.jena.sparql.engine.QueryIterator ;
import com.hp.hpl.jena.sparql.engine.binding.Binding ;
import com.hp.hpl.jena.sparql.lib.iterator.Iter;

/** Minus by materializing the RHS - this is not streamed on the right */
public class QueryIterMinus extends QueryIter2LoopOnLeft
{
    public QueryIterMinus(QueryIterator left, QueryIterator right, ExecutionContext qCxt)
    {
        super(left, right, qCxt) ;
    }

    @Override
    protected Binding getNextSlot(Binding bindingLeft)
    {
        boolean accept = true ;
        Set<Var> varsLeft = Iter.toSet(bindingLeft.vars()) ;

        for ( Iterator<Binding> iter = tableRight.iterator(null) ; iter.hasNext() ; )
        {
            Binding bindingRight = iter.next() ;
            
            if ( ! commonVariable(varsLeft, bindingRight) )
                continue ;
            if ( Algebra.compatible(bindingLeft, bindingRight) )
            {
                accept = false ;
                break ;
            }
        }

        if ( accept )
            return bindingLeft ;
        return null ;
    }

    private boolean commonVariable(Set<Var> varsLeft, Binding bindingRight)
    {
        for ( Iterator<Var> iter = bindingRight.vars() ; iter.hasNext() ; )
        {
            Var v = iter.next() ;
            if ( varsLeft.contains(v) )
                return true ;
        }
        return false ;
    }
}

/*
 * (c) Copyright 2007, 2008, 2009 Hewlett-Packard Development Company, LP
 * (c) Copyright 2010 Talis Systems Ltd
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */